/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.executiongraph.failover.flip1;

import org.apache.flink.configuration.Configuration;
import org.apache.flink.configuration.IllegalConfigurationException;
import org.apache.flink.configuration.JobManagerOptions;

import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * A utility class to load NG failover strategy factories from the configuration.
 */
public final class FailoverStrategyFactoryLoader {

	/** Config name for the {@link RestartAllFailoverStrategy}. */
	public static final String FULL_RESTART_STRATEGY_NAME = "full";

	/** Config name for the {@link RestartPipelinedRegionFailoverStrategy}. */
	public static final String PIPELINED_REGION_RESTART_STRATEGY_NAME = "region";

	private FailoverStrategyFactoryLoader() {
	}

	/**
	 * Loads a {@link FailoverStrategy.Factory} from the given configuration.
	 *
	 * @param config which specifies the failover strategy factory to load
	 * @return failover strategy factory loaded
	 */
	public static FailoverStrategy.Factory loadFailoverStrategyFactory(final Configuration config) {
		checkNotNull(config);

		// the default NG failover strategy is the region failover strategy.
		// TODO: Remove the overridden default value when removing legacy scheduler
		//  and change the default value of JobManagerOptions.EXECUTION_FAILOVER_STRATEGY
		//  to be "region"
		final String strategyParam = config.getString(
			JobManagerOptions.EXECUTION_FAILOVER_STRATEGY,
			PIPELINED_REGION_RESTART_STRATEGY_NAME);

		switch (strategyParam.toLowerCase()) {
			case FULL_RESTART_STRATEGY_NAME:
				return new RestartAllFailoverStrategy.Factory();

			case PIPELINED_REGION_RESTART_STRATEGY_NAME:
				return new RestartPipelinedRegionFailoverStrategy.Factory();

			default:
				throw new IllegalConfigurationException("Unknown failover strategy: " + strategyParam);
		}
	}
}
